Electrostatic upgrading of potash ores

ABSTRACT

The insoluble components of potash ores are substantially removed by electrostatic separation, the ore being first conditioned with an aliphatic amine of 8-22 carbon atoms or salts thereof, e.g. laurylamine, said amine being also preferably mixed with a carboxylic acid of 8-22 carbon atoms.

I Umted States Patent 1 1 3,591,093

[72] Inventors Robert Berthon [501 Field ofSearch 24l/15,20, Wittelsbeim (Haut-Rhin); 24, 79.1; 209/9, 11, 127, 128-131 Michel Bichara, Richwlller (Haut-Rhin), w f France [56] References Cited [21 Appl. No. 747,837 UNITED STATES PATENTS I 1 July 1963 2,762,505 9/1956 Lawyer 209/9 [451 6, 1971 2,927,010 3/1960 LeBaron. 209/9 x [731 Ass'gflee P P015 Alsace 3,073,443 1/1963 Snow 209/9 [32] P ,t 3,225,924 12/1965 Autenrieth 209/9 non y y [33 1 Fr FOREIGN PATENTS 31 115359 665,730 6/1963 Canada 209]]! Primary Examiner-Donald G. Kelly Attorney-Millen, Raptes & White [541 fgg T g g q 0F POTAS ORES ABSTRACT: The insoluble components of potash ores are bums o substantially removed by electrostatic separation, the ore [52] 11.8. CI 241/15, being first conditioned with an aliphatic amine of 822 car- 209/9, 241/24, 241/791 bon atoms or salts thereof, e.g. laurylamine, said amine being [5 l] Int. Cl ..B02c 19/12, also preferably mixed with a carboxylic acid of 822 carbon atoms.

ELECTROSTATIC UPGRADING OF POTASH ORES BACKGROUND OF THE INVENTION This invention relates to the treatment of potash ores con- 'taining insoluble impurities, and in particular to the electrostatic separation of a substantial portion of the insoluble impurities present in potash ores.

Potash ores generally contain insoluble impurities comprised of claylike materials often intermixed with insoluble compounds, such as anhydrite, carbonates, etc. Upon comminution of the ore, these claylike materials become subdivided into extremely fine particles which interfere with the separation of the desired components irrespective of the particular separation process used: wet methods such as froth flotation, sink-and-float process, heat-leaching coolingcrystallization, or dry methods such as electrostatic separation.

In particular, it has been observed that during froth flotation the claylike materials yield slimes which adsorb a large amount of relatively expensive flotation reagents. In addition, an appreciable part of these slimes is often found in the final concentrate, thereby decreasing the grade of the resultant product. In the heat-leaching cooling-crystallization processes, slimes deleteriously affect the crystallization of potash salts for they cause the formation of a large quantity of very fine crystals. In methods of sink-and-float or heavy-liquid separation, the insoluble impurities result in large variations of the density and of the viscosity of the separation heavy medium. Because the separation medium must, therefor, be freed of the slimes accumulated therein, special equipment is required for this purpose, and in any case, there is incurred an appreciable loss of heavy liquid.

Finally, in the case of electrostatic separation, it has been observed that the claylike impurities interfere with the electrification of ore particles preventing them from being charged with a sufficient selectivity to be separated with a satisfactory yield.

Different techniques are used for diminishing the detrimental effects of the insoluble impurities during the various separation procedures. However, such techniques can be applied only to ores having a relatively low content of insoluble materials. In most cases, therefore, it is necessary to submit the ores to a preliminary treatment to separate at least a major part of the insoluble ore impurities.

One of the first methods for decreasing the quantity of insoluble impurities is called desliming, which comprises treating the ores under strong agitation with water or brine, then separating out the slimy liquid from the ore. Apart from the fact that such a treatment is often incomplete, it results in the case of potash ores in an appreciable loss of valuable soluble salts. In addition, the treated ore must then be dried if it is to be submitted to a dry separation treatment. Because of these disadvantages, it has also been proposed to replace water by organic liquids in which the potash constituents of the ore are insoluble, but the cost of such an operation is still prohibitive due to solvent losses and because of the investment capital required for the large on-stream inventory of sol- ,a certain quantity of residual water. After this mild thermal treatment, the ore must be submitted to an electrostatic separation for which a roll-type apparatus is used, which secures a good contact between the particles to be separated and the conducting electrode. This process presents a serious disadvantage because it requires a very careful control of the temperature and of the water content of the treated ore. In addition, the output of a roll-type separator is small and its effectiveness for fine ore particles 100- 150 mesh Tyler is very low.

SUMMARY OF THE INVENTION A principal object of this invention, therefore, is to provide an improved process for desliming" potash ores.

Another object is to provide a preliminary treatment of potash ores which results in a product having a substantially lower quantity of insoluble material so that it is especially amenable to a subsequent beneficiation step for the separation of potassium salts.

Still another object is to provide a preliminary treatment of potash ores which results in a dry product, thereby facilitating a subsequent dry beneficiation step.

Upon further study of the specification and claims, other objects and advantages of the present invention will become apparent.

To attain the objects of this invention, the potash is subjected to a preliminary electrostatic separation. In this step the comminuted ore is first treated with an aliphatic amine having 8 to 22 carbon atoms, a salt of such amines or mixtures thereof, and preferably an aliphatic carboxylic acid having from 8 to 22 carbon atoms or mixtures of such acids. The resultant ore particles are then electrically charged and then submitted to the action of an electrostatic field in order to obtain a fraction leaner in insoluble impurities and a residue fraction richer in such impurities.

The aliphatic amines can be primary or secondary amines, saturated or unsaturated, containing 822 carbon atoms and, preferably the lower molecular weight amines containing 8- 16 carbon atoms. The amines can also be employed in the form of their salts, such as mineral acid and carboxylic acid salts, for example, the hydrochloride or acetate salts.

Among the amineswhich can be used, included but not limited thereto are those prepared from commercial fatty acids, either pure or technical grade, e.g. capryl-, lauryl-, myristyl-, palmityl-, stearyl-, oleylamine being perfectly suitable. Products of lower purity such as amines produced from naturally occuring fatty acid mixtures or those found in industrial residues or byproducts, for example, fatty amines of coprah, tallow, vegetable or animal oils, can also be used. Of course, it is also possible to utilize fatty amines prepared from petroleum chemicals.

As a carboxylic, all the fatty acids, saturated or unsaturated, cited above as raw materials for the preparation of amines, can be used in combination with at least one amine. Preferably, inexpensive products are chosen, for example, animal or vegetable oils such as linseed, soy bean and fish oil, which oils usually contain mixtures of fatty acids and esters thereof generally triglycerides.

In Canadian Pat. No. 665,730 the use of fatty amines alone or fatty acids alone has already been proposed for the beneficiation of potash ore by electrostatic separation, but in this patent the object of the separation was the direct obtention of concentrates enriched in valuable potash constituents and preferably of products having acceptable concentrations for commercial grades, that is containing at least 50 percent K 0. Sucha process is applicable to potash ores containing a sufficiently low quantity of slimes or insoluble impurities, but when the treated ore contains more than about 3-4 percent of impurities, concentrates having a sufficient K 0 content cannot be obtained.

In contrast, the object of the process of the invention is a treatment applicable to potash ores having relatively high impurity contents (at least about 4 percent the products so-obtained being amenable to an easier beneficiation of the valuable potash constituent. By using the process of the invention it has been observed that the product resulting from the electrostatic separation has a considerably reduced impurity content while its K, 0 content is not substantially modified. For example, a sylvinite ore containing initially 21 percent K, 0 (equivalent to 33.2 percent kcl) and 12 percent insoluble impurities was treated according to the invention; two fractions were obtained: a fraction containing 21 percent K, 0 and 5.l percent insoluble impurities, and a residue having a high content of insoluble materials (60 percent) which can be discarded because its potassium chloride (sylvite) content represents less than 4 percent of the initial K total K 0 or sylvite content of the ore.

The reagent can be utilized in natural undiluted form, but preferably is dissolved in an organic solvent having no effect on the separation, such as, for example, hexane, benzene, tn'chlorethylene. The use of the reagents in the form of an aqueous solution or dispersion is preferably avoided, for the presence of water tends to form agglomerates or to subdivide the insoluble materials. These two phenomena interfere with the electrostatic separation treatment and favor the accumulation of potassium chloride in the insoluble fraction. When using the combination amine reagent-acid reagent, these can be added either separately or in the form of a mixture and, as mentioned hereabove, in their natural state or dissolved in an organic solvent.

The total quantity of reagents used is about from to 1000 g./t. (grams per metric ton) of treated ore and, within this range, the optimum quantity obviously depends on the nature of the ore and its impurity content. in certain cases, the amine reagent alone is sufficient to obtain satisfactory results, in particular when the amines used have a relatively low molecular weight as, for example, laurylarnine. However, it is particularly advantageous to reinforce the action of amine reagent by addition of the acid reagent. Under these conditions the proportion of the acid relative to the total quantity of reagent is generally lower than 50 percent, and preferably about l0-30 percent by weight.

Aside from those mixtures of amines and acids specifically described in the examples, the following are also preferred. All of the fatty amines such as the amines commercially available from Armour and Company under the trade name Armeens can be used, and preferably those containing less than 16 carbon atoms. lln addition to the natural oils or fats mentioned above, carboxylic acids such as caprylic, capric, lauric, myristic, palmitic, oleic, linoleic or stearic acid are suitable and can be associated with any of the cited amines.

in contrast with some methods which require the use of a roll-type separator, it is possible, in the practice of this invention, to use either such a device or a free-fall type separator, wherein the particles fall free. Moreover, the free-fall type is generally preferred because its output is higher and its effectiveness greater, particularly for separating fine particles. By operating according to this invention in the latter type of separator, a relatively low field strength, lower than 2000 V/cm. is sufficient, the operation being preferably effected between about 800 and 1500 V/cm. When a combination of amine and acid is utilized as the reagent, the preferred field strength is 800-1000 V/cm. Higher field strength must be avoided in order to obtain an insoluble residue as poor as possible in valuable potash constituent which can be discarded without any subsequent treatment for recovering these potash values.

For conducting the process, the ore is first comminuted by usual methods. The comminution which is intended to liberate the valuable constituents of the treated ore must also sufficiently reduce the particle size of the treated product, so that the electrostatic treatment can be conducted efficiently. In industrial practice, the ore is comminuted at least sufficiently to obtain the liberation of the different constituents, but in any case so that its particle size does not exceed about 2 mm. (9 mesh Tyler). It is advisable that the particle size does not exceed this value, for when the particles are too large, due to their weight they escape the action of electrostatic forces. The process does not, however, require that the particle size be comprised of a very narrow range, which is in contrast to known methods in which the separation is not selective for fine particles. Since the present process allows a good yield even with fine particles having, for example, a size of about l50-l00 mesh, the preferred particle size range is 9 to +150 mesh. It is advantageous in any case that the proportion of extremely fine particles 150 mesh) be as low as possible, e.g. less than 10 percent.

The comminuted ore, optionally preliminarily dried, is then conditioned as described hereabove. The operation is performed, for example, in a horizontal rotary drum or in any other type of mixer capable of effecting a good distribution of the reagents on the treated particles. The conditioning can also be effected by spraying the reagents on the comminuted ore. The conditioned product is then heated to a temperature usually of about 60- 100 C. so as to dry and remove the solvent when the reagents have been added in form of an organic solution.

The dried product is charged, for example, by contact electrification, this charging taking place also at a temperature comprised between about 60 to 100 C., preferably about 60 to C. Since drying and charging can be effected in the same range of temperature, it is possible to operate in the same vessel and in a single stage, for example, by means of heated air flowing through a rotary drum or by maintaining the product in form of a fluidized bed.

With respect to the optional preliminary drying, although in most cases such a treatment is not indispensable, it may become necessary when treating particularly wet and dirty ores. Generally such drying is conducted at to 150 C. For example, a preliminary drying at C. of an ore containing 18.6 percent of insoluble material has considerably improved the subsequent separation: the quantity of insoluble material present in the residue which was 27.6 percent without any drying reached 44.7 percent after drying.

The ore prepared as described hereinabove is then fed into an electrostatic separator. The advantageous electrostatic separation temperature is generally 40'80 C., preferably 6070 C. depending on the chosen reagents and the treated ore composition. It is also to be noted that when climatic conditions are severe, the ore might cool down too quickly between the charging and the electrostatic separation itself. Consequently, the time period between these two operations must be made as short as possible, or, otherwise the ore must be heated just before its feeding into the separator. Generally speaking, all convenient measures must be taken to obtain the desired ore temperature in the electrostatic separator.

Three fractions are collected at the outlet of the separator: the ore having a lower content in insoluble impurities which is ready for the subsequent treatment of recovering the valuable constituents, a fraction of middlings to be recycled, and a fraction containing the major part of impurities initially present in the ore.

The present invention is especially applicable to those potash ores having at lest 4 percent, preferably at least 6 percent, and preferably 10 percent by weight and more insoluble material.

Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The following preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the specification and claims in any way whatsoever.

EXAMPLES An ore containing 20.7 percent of K 0 and 12.1 percent by weight of insoluble material was comminuted to a particle size lower than 1.2 mm. (14 mesh (Tyler and then individual portions thereof were admixed with single hexane solutions containing 10 percent of the respective reagent given in the following table. The product was then passed to a substantially horizontal rotating drum through which flowed a hot airstream for drying the product and removing the solvent. The dry ore, electrically charged during its travel through the drum, left the latter at an average temperature of 70 C., and was passed through a feeder (vibratory trough) into a free-fall type separator having between its electrodes an electric field of 1000 V/cm.

At the outlet of the separator three fractions were collected: a concentrate, middlings to be recycled, and a residue containing the major portion of the initial insoluble impurities.

The following table shows the results obtained by one single pass through the separator with different reagents:

' purities in the product is further decreased and the concentration of insoluble impurities in the residue is further increased.

('oncentrnt Residue Quantity of Insoluble lnsolnblv reagents, g. t. Weight, K20, materials, Weight, K10, materials, Reagents percent percent percent percent percent percent Laurylamine (LA)... 250. 77 18. 7 6. 3 7. 21. 1 46. 6 LA plus t-aprylic acid 250 plus 50 80 19. 8 6. 3 7.0 17. 7 52. 2 LA plus soy bean oil 200 plus 50. til 20. 1. 6.0 7. 16. 6 54. 6 LA plus lish oil. 200 plus 50. 84 21. 2 5. 3 7.0 12. '2 59. 9 LA plus ncids GIG-C2: 200 plus 50. 85 19. 2 4. J 5. 0 18. 5 53. 8

In the first test conducted with laurylamine alone as conditioning agent, the resulting concentrate contained a quantity of insoluble materials, materially reduced relative to the initial content of the treated ore. Theother four tests show that the association of a fatty acid or a fatty acid mixture with the aminated reagent notably improves the selectivity of the separation.

The preceding examples can be repeated with similar success by substituting the generically or specifically described reactants and/or operating conditions of this invention for those used in the preceding examples.

From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention, and without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions. Consequently, such changes and modifications are properly, equitably, and intended to be, within the full range of equivalence of the following claims.

What we claim is:

l. in a process for the treatment of sylvinite ore containing an original concentration of sylvite, expressed as K 0 and at least 4 percent by weight insoluble impurities, the improvement of removing said insoluble impurities from said ore prior to separating soluble ore components from one another, said removing comprising:

a. comminuting the ore to a particle size of less than 9 mesh;

b. treating the comminuted ore with a reagent comprising at least 50 percent by weight of at least one member selected from the group consisting of an aliphatic amine of 8-22 carbon atoms and a salt thereof;

c. inducing an electric charge on resultant treated ore;

d. subjecting resultant charged ore to electrostatic separation under a field strength of less than 2000 V/cm; and

e. recovering from said electrostatic separation a product substantially reduced in the concentration of insoluble impurities and a residue substantially increased in the concentration of insoluble impurities as compared to said original concentration in the ore, the concentration of K, 0 in both the product and treated are being substantially the same.

2. A process as defined by claim 1 wherein said aliphatic amine contains 8- 16 carbon atoms.

3. A process as defined by claim 1 wherein said aliphatic amine is laurylamine.

4. A process as defined by claim 1 wherein said reagent comprises in addition aliphatic carboxylic acid of 8-22 carbon atoms and whereby the concentration of insoluble impurities in the product is further decreased and the concentration of insoluble impurities in the residue is further increased.

5. A process as defined by claim 2, wherein said reagent comprises in addition an aliphatic carboxylic acid of 8-22 carbon atoms, and whereby the concentration of insoluble im- 6. A process as defined by claim 3, wherein said reagent comprises in addition an aliphatic carboxylic acid of 8-22 carbon atoms, and whereby the concentration of insoluble impurities K, 0 in the product is further decreased and the concentration of insoluble impurities in the residue is further increased.

7. A process as defined by claim 4 wherein said acid is present in said reagent in a concentration of 10-30 percent byweight.

8. A process as defined by claim 6 wherein said acid is present in said reagent in a concentration of 10-30 percent by weight.

9. A process as defined by claim 7 wherein said field strength is about 800-1000 V/cm.

10. A process as defined by claim 8 wherein said acid portion is a member selected from the group consisting of caprylic acid, soy bean oil, fish oil, and acid having 18-22 carbon atoms.

11. A. process as defined by claim 1 wherein the comminuted ore is treated with -1000 g./t. of said reagent.

12. A process as defined by claim 4 wherein the comminuted ore is treated with 100-1000 g./t. of said reagent.

13. A process as defined by claim 3 wherein said field strength is about 1000-1500 V/cm.

14. A process as defined by claim 1, wherein said insoluble impurities comprise at least 6 percent by weight of said potash ore.

15. A process as defined by claim 1 wherein said insoluble impurities comprise at least 10 percent by weight of said potash ore.

16. In a process for the treatment of sylvinite ore an original concentration of insoluble impurities, the improvement of removing said insoluble impurities from said ore prior to separating soluble ore components from one another, said removing comprising:

a. comminuting the ore to a particle size of less than 9 mesh;

b. treating the comminuted ore with a reagent comprising about 10-30 percent by weight of an aliphatic carboxylic acid of 8-22 carbon atoms, and at least 50 percent by weight of at least one member selected from the group consisting of an aliphatic amine of 8-22 carbon atoms and a salt thereof;

c. inducing an electric charge and resultant treated ore;

d. subjecting resultant charged ore to an electrostatic separation under a field strength of less than 2000 V/cm.; and

. recovering from said electrostatic separation a product substantially reduced in the concentration of insoluble impurities and a residue substantially increased in the concentration of insoluble impurities, as compared to said original concentration in the ore.

17. A process as defined by claim 16 wherein said field strength is about 800- 1000 V/cm.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Paten 3, 559L093 Dated July 6 1971 Invent fls) Robert Berthon Wittelsheim et a1 It is certified that error appears in the above-identified patent: and that said Letters Patent are hereby corrected as shown below:

In the Sgecification:

Col. 3, line 17, after "from" and before "to" please insert --l00-;

Col. 4, line 3 in the Example, "(14 mesh Tyler" should read --(14 mesh Tyler)--.

In the Claims:

Claim 16, line 1, after "ore" and before an original" please insert --containing---.

Signed and sealed this 11th day of July 1972.

(SEAL) Attest:

EDWARD M.FLETCIER, JR. ROBERT GO'ITSCHALK Attesting Officer Commissioner of Patents FORM (O-69] USCOMM-DC 00376-P69 u s. sovzmmzwr wnnmus ornc: nu o-au-au 

2. A process as defined by claim 1 wherein said aliphatic amine contains 8-16 carbon atoms.
 3. A process as defined by claim 1 wherein said aliphatic amine is laurylamine.
 4. A process as defined by claim 1 wherein said reagent comprises in addition aliphatic carboxylic acid of 8-22 carbon atoms and whereby the concentration of insoluble impurities in the product is further decreased and the concentration of insoluble impurities in the residue is further increased.
 5. A process as defined by claim 2, wherein said reagent comprises in addition an aliphatic carboxylic acid of 8-22 carbon atoms, and whereby the concentration of insoluble impurities in the product is further decreased and the concentration of insoluble impurities in the residue is further increased.
 6. A process as defined by claim 3, wherein said reagent comprises in addition an aliphatic carboxylic acid of 8-22 carbon atoms, and whereby the concentration of insoluble impurities K2 0 in the product is further decreased and the concentration of insoluble impurities in the residue is further increased.
 7. A process as defined by claim 4 wherein said acid is present in said reagent in a concentration of 10-30 percent by weight.
 8. A process as defined by claim 6 wherein said acid is present in said reagent in a concentration of 10-30 percent by weight.
 9. A process as defined by claim 7 wherein said field strength is about 800-1000 V/cm.
 10. A process as defined by claim 8 wherein said acid portion is a member selected from the group consisting of caprylic acid, soy bean oil, fish oil, and acid having 18-22 carbon atoms.
 11. A process as defined by claim 1 wherein the comminuted ore is treated with 100-1000 g./t. of said reagent.
 12. A process as defined by claim 4 wherein the comminuted ore is treated with 100-1000 g./t. of said reagent.
 13. A process as defined by claim 3 wherein said field strength is about 1000-1500 V/cm.
 14. A process as defined by claim 1, wherein said insoluble impurities comprise at least 6 percent by weight of said potash ore.
 15. A process as defined by claim 1 wherein said insoluble impurities comprise at least 10 percent by weight of said potash ore.
 16. In a process for the treatment of sylvinite ore an original concentration of insoluble impurities, the improvement of removing said insoluble impurities from said ore prior to separating soluble ore components from one another, said removing comprising: a. comminuting the ore to a particle size of less than 9 mesh; b. treating the comminuted ore with a reagent comprising about 10-30 percent by weight of an aliphatic carboxylic acid of 8-22 carbon atoms, and at least 50 percent by weight of at least one member selected from the group consisting of an aliphatic amine of 8-22 carbon atoms and a salt thereof; c. inducing an electric charge and resultant treated ore; d. subjecting resultant charged ore to an electrostatic separation under a field strength of less than 2000 V/cm.; and e. recovering from said electrostatic separation a product substantially reduced in the concentration of insoluble impUrities and a residue substantially increased in the concentration of insoluble impurities, as compared to said original concentration in the ore.
 17. A process as defined by claim 16 wherein said field strength is about 800-1000 V/cm. 